The present invention relates to bedding, and particularly to combinations of an innerspring mattress with a quilted mattress cover.
An immense expenditure is laid out for mattresses each year. Some of this expenditure goes for air, water, or foam mattresses, but (in the United States at least) the overwhelming majority of expenditure goes for innerspring mattresses.
Some mattress technologies provide support which is inherently somewhat uniform (e.g. waterbeds, as extensively discussed in the presently preferred embodiment). This is NOT true of innerspring mattresses, where different coils can be made of different stiffnesses, to modulate the hardness of the mattress as desired across the length and width of the mattress. However, many existing innerspring mattresses were manufactured without such modulation, or without an adequate amount of such support modulation.
An innerspring mattress is a moderately expensive and long-lived consumer asset. (A typical price for a good-quality mattress and box-spring set, in the United States, would be in excess of $500, and the in-service lifetime of such a set would typically be more than 10 years.) Thus, purchase of complete bedding sets for all beds in a household would typically be a sizable expenditure. Consumers will be reluctant to replace old mattresses which are still serviceable.
One advantageous application of the disclosed innovations is that they can be used to retrofit improved postural support to an existing innerspring mattress.
A further related advantage of the disclosed innovations is that manufacturers can use these innovative teachings to rapidly modify existing mattress designs, which are already in production (or even in inventory), to improve the postural support at minimal cost.
A further advantage is that a mattress's postural support can be readily customized. Thus, for example, the distribution of support needed by a muscular male athlete is quite different from that needed by a fashionably thin nulliparous adult female, or an obese middle-aged person. By use of the disclosed innovations, customized versions can readily be produced, at minimal cost, as simple modifications to an existing production line.
The hardness of an innerspring mattress is affected by the gauge of the spring wire, the number of springs, and the coil design. There is no generally accepted quantitative measure of hardness or softness of innersprings, but the extreme cases can be readily identified. Thus, for example, a full-size mattress with 312 coils.sup.1 of 12.5 gauge spring wire in Bonnell wrap would be an unusually hard mattress. Mattresses with lighter-gauge spring wire, for a given number of coils, would be softer. For a given spring wire gauge, mattresses with a lower number of coils will generally be softer. FNT .sup.1 The number of coils is usually specified with reference to the full-size mattress. For a given mattress model, this number is varied proportionately for other mattress sizes.
Harder innerspring mattresses provide better overall postural alignment. However, harder mattresses are more likely to create pressure points. The disclosed innovations provide a way to reconcile these choices, and to obtain the comfort benefits of a soft mattress and also the postural advantages of a hard mattress.
Uniform support presents a problem, because the weight distribution of the human body is not at all uniform. The highest concentration of mass (per unit length in the height axis) will be between the shoulder blades and the hips. The mass per unit length is generally lower at the head, and is much lower in the legs..sup.2 Thus, if a soft mattress has a uniform thickness and support, the user's hips or buttocks will tend to sink excessively far into the mattress..sup.3 This problem is exacerbated when the mattress is used by two persons sleeping together. FNT .sup.2 The weight distribution is, of course, different from person to person, depending on the person's age, height, sex, obesity, and general body type. However, the problems discussed are problems for a very large fraction of users. FNT .sup.3 Spinal alignment, in a good sleeping posture, should be the same as that in a good standing posture. Thus, a sleeper should be supported so that his or her spine will be laterally straight, and will be curved with no more (and no less) than normal lumbar and thoracic arch and pelvic tilt. Distortions of this sleeping posture will produce immediate or gradual discomfort, and may not be optimal for the sleeper's health.
This deficit in support will tend to reduce the user's comfort, to a greater or lesser degree depending on the user. However, a more important effect is that this deficit in support may permit a user to sleep in a condition of postural misalignment. This may lead to backaches, or to vague discomforts which reduce the user's overall level of health and well-being.
Some efforts have been made to increase the support under the torso..sup.4 Apart from the art of waterbeds, other attempts have been made to design sleeping pads with some allowance for the uneven weight distribution of the human body. Many of these attempts have used convoluted foam,.sup.5 which is one of the basic structural materials used in designing bedding structures. FNT .sup.4 For example, the "System 750" waterbed, from Land and Sky, includes a floating foam/fiber structure, inside the bag, which is thicker under the user's midsection to provide additional back support. FNT U.S. Pat. No. 5,077,848 (to McDaniel et al.) discloses an immersed tube structure, with foam inserts in the tube.
The "Avanti III" model, from Pleasant Rest, is a waterbed with a foam topping, which includes extra layers of fiber (under a single sheet of foam) under the user's midsection to provide added lumbar support.
The "Marvelous Middle" from Restonic includes stiffer springs in the middle of the mattress. The cover itself includes extra lines of stitching, under the sleeper's midsection, which give the impression that the middle of the cover is different from the rest of the cover; but in fact (insofar as is known to the present inventor) the cover is uniform over its length, and does NOT include any additional material under the sleeper's midsection. FNT .sup.5 Convoluted foam (in which one surface is carved into a rippled or egg-carton shape) is effectively softer than a solid block of foam of equivalent height, because the individual protrusions in the carved portion have more room to expand laterally under pressure. Convoluted foam is described, for instance, in U.S. Pat. No. 3,026,544 to Persicke et al., which is hereby incorporated by reference. FNT Some of the attempts to use convoluted foam pads for sleeping structures are shown in U.S. Pat. No. 4,620,337 to Williams et al.; 4,955,096 to Gilroy et al.; and 4,879,776 to Farley; all of which are hereby incorporated by reference.